3. Physical hazard
Leaving gas can next to a furnace, likely to produce a fire or explosion, is an example of a Physical hazard.
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Physical hazard is an agent, factor, or circumstance that can cause injury when coming in contact. It include ergonomic hazards, radiation, heat and cold stress, vibration hazards, explosion and noise hazards.
Example: Leaving gas can next to a furnace is likely to produce a fire or explosion.